1. Field of the Invention
The present invention relates to an LED lamp employing an LED chip that is a semiconductor light emitting device as a light source specifically provided with the object of providing LED lamp configuration applicable to uses in vehicle signal lights etc. demanding area-lighting with uniform brightness.
2. Description of Related Art
An example configuration of a related type of LED lamp 90 is shown in FIG. 6. An LED chip 91 is mounted within a horn section 92a provided in order to obtain reflection at a lead frame 92, light is reflected in a prescribed direction and the LED chip 91 is covered by a molded case 93 of transparent resin.
The object of the molded case 93 is to provide resistance to moisture and to provide light from the LED chip 91 including light reflected at the horn section 92a at an appropriate illuminating angle. A top part 93a of the molded case 93 therefore forms a convex lens and an illuminating angle .gamma. of, for example, 30 to 40 degrees is provided.
In the related LED lamp 90 of the above configuration, the LED chip 91 is embedded within the molded case 93. The LED chip 91 is therefore subjected to stress due to the difference in the thermal expansion coefficients of the LED chip 91 and the molded case 93, and it is therefore extremely important to make the diameter of the molded case 93 approximately 5 mm or less.
When the LED lamp 90 is used as a light source for a vehicle light such as a rear light, a plurality of LED lamps 90 are adopted. However, the light emitting area of one LED lamp 90 is small and the illuminating angle is narrow. There is also a strong tendency for the luminance distribution to focus itself about a central line. It is therefore preferable to arrange a plurality of LED lamps 90 at a narrow pitch in order to provide a uniform intensity of illumination at the outer lens surface of a vehicle light.
However, if LED lamps are arranged in a small pitch at the rear surface of an outer lens of a vehicle light having a prescribed area, the number of LED lamps 90 required increases, which causes increasing costs. Further, when the pitch of the LED lamps 90 is narrow, the temperature within a light housing for the vehicle light increases, and the luminance of the LED lamps 90 decreases.
Further, there is a tendency of oversimplification for the vehicle lamp comprising the conventional LED lamp 90. Since the mold case 93 is a convex lens which must act as an optical means to obtain prescribed optical characteristics of the LED lamp 90, it is difficult for the mold case 93 to have any complicated shape such as a combination of pentagons, although such a complicated shape is required from aesthetic appearance of the vehicle light.
It is therefore the object of the present invention to provide an LED lamp that overcomes the above problems and which is applicable to uses in vehicle signal lights etc. demanding uniform brightness.